title: Estimates of pandemic influenza vaccine effectiveness in Europe, 2009-2010: results of Influenza Monitoring Vaccine Effectiveness in Europe (I-MOVE) multicentre case-control study.
abstract: BACKGROUND
  A multicentre case-control study based on sentinel practitioner surveillance networks from seven European countries was undertaken to estimate the effectiveness of 2009-2010 pandemic and seasonal influenza vaccines against medically attended influenza-like illness (ILI) laboratory-confirmed as pandemic influenza A (H1N1) (pH1N1).
  
  
  RESULTS
  Sentinel practitioners swabbed ILI patients using systematic sampling. We included in the study patients meeting the European ILI case definition with onset of symptoms >14 days after the start of national pandemic vaccination campaigns. We compared pH1N1 cases to influenza laboratory-negative controls. A valid vaccination corresponded to >14 days between receiving a dose of vaccine and symptom onset. We estimated pooled vaccine effectiveness (VE) as 1 minus the odds ratio with the study site as a fixed effect. Using logistic regression, we adjusted VE for potential confounding factors (age group, sex, month of onset, chronic diseases and related hospitalizations, smoking history, seasonal influenza vaccinations, practitioner visits in previous year). We conducted a complete case analysis excluding individuals with missing values and a multiple multivariate imputation to estimate missing values. The multivariate imputation (n = 2902) adjusted pandemic VE (PIVE) estimates were 71.9% (95% confidence interval [CI] 45.6-85.5) overall; 78.4% (95% CI 54.4-89.8) in patients <65 years; and 72.9% (95% CI 39.8-87.8) in individuals without chronic disease. The complete case (n = 1,502) adjusted PIVE were 66.0% (95% CI 23.9-84.8), 71.3% (95% CI 29.1-88.4), and 70.2% (95% CI 19.4-89.0), respectively. The adjusted PIVE was 66.0% (95% CI -69.9 to 93.2) if vaccinated 8-14 days before ILI onset. The adjusted 2009-2010 seasonal influenza VE was 9.9% (95% CI -65.2 to 50.9).
  
  
  CONCLUSIONS
  Our results suggest good protection of the pandemic monovalent vaccine against medically attended pH1N1 and no effect of the 2009-2010 seasonal influenza vaccine. However, the late availability of the pandemic vaccine and subsequent limited coverage with this vaccine hampered our ability to study vaccine benefits during the outbreak period. Future studies should include estimation of the effectiveness of the new trivalent vaccine in the upcoming 2010-2011 season, when vaccination will occur before the influenza season starts.
authors.affiliation: EpiConcept, Paris, France. m.valenciano@epiconcept.fr
authors.forename: Marta
authors.initials: M
authors.lastname: Valenciano
authors.forename: Esther
authors.initials: E
authors.lastname: Kissling
authors.forename: Jean-Marie
authors.initials: JM
authors.lastname: Cohen
authors.forename: Beatrix
authors.initials: B
authors.lastname: Oroszi
authors.forename: Anne-Sophie
authors.initials: AS
authors.lastname: Barret
authors.forename: Caterina
authors.initials: C
authors.lastname: Rizzo
authors.forename: Baltazar
authors.initials: B
authors.lastname: Nunes
authors.forename: Daniela
authors.initials: D
authors.lastname: Pitigoi
authors.forename: Amparro
authors.initials: A
authors.lastname: Larrauri Cámara
authors.forename: Anne
authors.initials: A
authors.lastname: Mosnier
authors.forename: Judith K
authors.initials: JK
authors.lastname: Horvath
authors.forename: Joan
authors.initials: J
authors.lastname: O'Donnell
authors.forename: Antonino
authors.initials: A
authors.lastname: Bella
authors.forename: Raquel
authors.initials: R
authors.lastname: Guiomar
authors.forename: Emilia
authors.initials: E
authors.lastname: Lupulescu
authors.forename: Camelia
authors.initials: C
authors.lastname: Savulescu
authors.forename: Bruno C
authors.initials: BC
authors.lastname: Ciancio
authors.forename: Piotr
authors.initials: P
authors.lastname: Kramarz
authors.forename: Alain
authors.initials: A
authors.lastname: Moren
mesh_terms: D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D005060:Europe / Q000453:epidemiology; D005260:Female; D006801:Humans; D007223:Infant; D053118:Influenza A Virus, H1N1 Subtype; D007252:Influenza Vaccines; D007251:Influenza, Human / Q000453:epidemiology / Q000517:prevention & control* / Q000821:virology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016017:Odds Ratio; D017063:Outcome Assessment, Health Care; D058873:Pandemics / Q000517:prevention & control; D018571:Sentinel Surveillance; D055815:Young Adult
chemical_list: D007252:Influenza Vaccines